Lol, I remember seeing you battle with Roserade; and even back then the team was pretty solid. With Hippo and Forre, the team is really great and has good synergy. The only problems I can see here is a slight weakness to powerful setup sweepers with coverage- Thundurus-T being a big and obvious one, with Reuniclus and some Sun Sweepers on the list as well. I know you really like Heal Bell on Celebi, but I agree with many others that Perish Song over Heal Bell is a great idea. Heal Bell doesn't seem as useful as your team doesn't really mind TSpikes or status- half your team is immune to Toxic, you have a Spinner to spin away Toxic Spikes, and you have a Magic Coater and a Natural Healer- so your team doesn't mind status much. Perish Song can at least be used to force out setup sweepers that can beat Heatran and Hippo, as well as Baton Pass teams, who could also give you problems, passing to Espeon to relect your phazing attempts. Speaking of Espeon, it seems as if some particular Magic Bouncers (obv Xatu / Espeon) can sit their butts down and just reflect everything you try to throw at them. Espeon can heal itself with Recover and Calm Mind in your face; it can survive a BBird and Recover off a U-Turn. Being able to force Espeon out with Celebi will definitely be a huge help.
Being that Psychic / Ghost types like Xatu / Espeon / Reuniclus / Lati@s / Gengar can be quite troubling, since each of them can either reflect / escape your stall attempts or just pummel your team to death with STABs and coverage. Just to give you a little just-in-case tool, you could try Shadow Ball over Scald on Jellicent. This hits those Psychic types pretty hard even without any SpA investment; not enough to sweep anything but at least enough to prevent setup / speed up stall process. Scald is useful at times to hit through Fire types, but Hippo does that even better, and Heatran can wall most Fire / Steel types and Stall them to death anyway. Also, because you have WoW already, the burn from a scald is no longer necessary.
Now for an even tinier nitpick, your spread for Crobat is no longer as efficient now that your team doesn't carry Spikes; a spread of 186 HP / 144 Atk / 176 Spe Jolly might be better; this lets you OHKO Keldeo even after SR. This spread also does something neat in that it 2HKO's 252 HP Espeon with U-Turn, which is always nice. It lets you 2HKO Latios after SR with UTurn as well. This all are very minute differences, but they can help, so I'd suggest you try them. Crobat's bulk isn't that great anyway so you won't be dieing to any more hits.
Now for a more optional change; your team is weak to Duggy Sun so to help with that you can use Air Balloon instead of Leftovers on Heatran. However, it's a small threat, and Lefties is better on pretty much everything else, so it's up to your own preference.
I'm being really picky because your team is extremely solid. There is a lot of great defensive synergy in your team, which is great for a stall team such as yours. Hopefully at least one of these suggestions help.
Good luck, my friend!